Python字符串join（）方法

Python string join() method creates a string from an iterable. It joins all the iterable elements with the string as delimiter and returns it.

Python字符串join（）方法从可迭代对象创建一个字符串。它将所有可迭代的元素与字符串作为分隔符相连并返回它。

什么时候使用Python String join（）方法？ (When to use Python String join() Method?)

Some possible use cases are:

一些可能的用例是：

Creating CSV String from an iterable such as List, Tuple, etc.从列表，元组等迭代对象创建CSV字符串。
For logging purpose, get the string representation of the iterable and log into file.为了进行日志记录，请获取iterable的字符串表示形式并登录到文件中。
Saving an iterable object into a file by converting it to a string.通过将可迭代对象转换为字符串，将其保存到文件中。

join（）方法的语法 (Syntax of join() Method)

The join() method syntax is:

join（）方法的语法为：

str.join(iterable)

The output is a new string, which we can assign to another variable. We can use List, Tuple, String, and Set as input data types because they are iterables.

输出是一个新字符串，我们可以将其分配给另一个变量。我们可以使用List，Tuple，String和Set作为输入数据类型，因为它们是可迭代的。

Let’s look at some examples of using string join() method.

让我们看一些使用字符串join（）方法的示例。

1.将字符串列表连接到CSV (1. Joining List of Strings to CSV)

delimiter = ","csv_str = delimiter.join(['a', 'b', 'c'])print(csv_str)  # a,b,c

2.字符串的串联 (2. Concatenation of the Strings)

tuple_vowels = ('a', 'e', 'i', 'o', 'u')vowels_str = "".join(tuple_vowels)print(vowels_str)  # aeiou

We can use join() with an empty string to concatenate all the strings in the iterable.

我们可以使用带有空字符串的join（）来串联可迭代对象中的所有字符串。

3.将join（）与单个字符串一起使用作为输入 (3. Using join() with Single String as input)

str = 'Hello'print(f'String characters are: {",".join(str)}')

Output:

输出：

String characters are: H,e,l,l,o

The string is iterable in Python. So when we pass a single string as join() method input, its characters are the iterable elements.

该字符串在Python中是可迭代的。因此，当我们传递单个字符串作为join（）方法输入时，其字符是可迭代的元素。

4.字符串与set（）的join（） (4. String join() with Set)

vowels_set = set(('a', 'e', 'i', 'o', 'u'))print(" ".join(vowels_set))

Output:

输出：

u i e o a

Python set is an unordered collection, so the iteration order is random. You might get a different output in multiple runs.

Python set是无序集合，因此迭代顺序是随机的。您可能会在多次运行中获得不同的输出。

5. join（）的异常 (5. Exception with join())

If the iterable elements are not string, it raises a TypeError.

如果可迭代元素不是字符串，则引发TypeError。

class Data:passd1 = Data()
d2 = Data()list_data = [d1, d2]print(",".join(list_data))

Output:

输出：

TypeError: sequence item 0: expected str instance, Data found

结论 (Conclusion)

The join() method is useful in creating a string representation from the iterable elements. This method returns a new string and the original string and iterable remains unchanged. We can create CSV string as well as a tab-separated string using this method.

join（）方法在根据可迭代元素创建字符串表示形式时很有用。此方法返回一个新字符串，原始字符串和可迭代保持不变。我们可以使用此方法创建CSV字符串以及制表符分隔的字符串。

进一步阅读 (Further Reading)

Python String FunctionsPython字符串函数
f-strings in PythonPython中的f字符串
String formatting in PythonPython中的字符串格式

翻译自: https://www.journaldev.com/23571/python-string-join